Dan

Appreciate all you say as I too train operators.

In regard to the steer wheel lift off I explain to operators that if that is happening they are lifting 40% to much - 1400 kg when they should only be lifting 1000 kg. And that the result of overloading is that the forklift will tipover even more readily.

Consider the 78" carpet prong mentioned - would probably have a 40" load centre. The 100 lb per inch rule would say reduce the capacity by 1600 lb.

So for a 2000 lb forklift the predicted capacity would be 400 lb. The actual capacity would be over 1400 lb.

But for a 10000 lb forklift the predicted capacity would be 8400 lb but the actual capacity would be only 7100 lb. At 8400 lb it would be around 20% overloaded.

My suggestion for you if you beleive that you need a "X lb per inch" would be to relate it to truck size say:
2000 lb - 3500 lb 50 lb/in
4000 lb - 6500 lb 100 lb/in
7000 lb - 8000 lb 150 lb/in
9000 lb - 12000 lb 200 lb/in...

You'd have to do your own risk assessment and develop your own values for the rules keeping in mind that if there was a serious incident that resulted from someone using your rules you might be drawn into litigation.